300 blood samples from individuals will be assayed at the Roswell Park Memorial Institute, and duplicates of these samples will be assayed at the M.D. Anderson Hospital. These samples will be obtained from 150 lung cancer patients and 150 control subjects, of which half will be smokers and half non-smokers. In addition, in a sub-set of 50 persons, results will be compared in the two laboratories when the same individual is sampled three to five separate times. Approximately 200 of the above samples will be drawn at Roswell Park Memorial Institute for assays in both laboratories, and 100 samples will originate at the M.D. Anderson Hospital. Blood samples will be coded before they are cultured and assayed at the Contractor's laboratories or sent to M.D. Anderson Hospital.